Traditional printing technology, especially lithographic printing, employs printing plates to produce a printed image on a printing medium or substrate such as a paper. These printing plates may be produced with various imaging technologies such as computer-to-plate (CTP) or computer-to-film (CTF) imaging technology. In CTP imaging technology, an image to be printed may be created as a computer file and output directly to the printing plate. In CTF technology, the computer file representing the image is first output to a transparent film. The transparent film is then used to expose the printing plate. CTF technology is older. Modem printing processes increasingly use CTP technology because it removes a stage in the printing process. Regardless of the type of printing plate technology used, the image to be printed is rendered on the printing plate in the form of a pattern of “dots” having a predetermined density. The dots make up the printed image. Generally, one printing plate for each basic printing color (cyan, magenta, yellow and black) is employed to form the final printed full color image on the printing medium. Each different color printing plate will have a predetermined dot pattern thereon representing that color's contribution to the final full color image.
Traditional or “legacy” CTP printing plates have a high contrast between areas of exposure and non-exposure or, respectively, imaged and non-imaged portions of the printing plate. The high contrast may be achieved through diffuse illumination to provide uniform lighting of the medium to be measured, which may be referred to herein as a measurable medium and/or an imaging member, for example. Uniform lighting may be employed to better distinguish a suitable threshold setting between the exposed and non-exposed areas of the printing plate or imaged and non-imaged areas of the printing plate, respectively. The areas of interest on the CTP printing plates may be referred to as “targets” and the act of probing the target may be referred to as “targeting.” The target may comprise image areas as well as non-image areas. In general, the target may be illuminated using a variety of illumination sources. The illumination sources for targeting may include red, green and blue (RGB) and white colored sources depending on the color of the CTP printing plate to be measured. Some devices for targeting the CTP printing plates may employ a physical reticule or targeting element configured for placement over or around a desired high contrast target for which dot coverage is to be measured. Measuring dot coverage may comprise, for example, measuring the size, spacing or angle of the dots that make up a printed image.
CTP printing plates utilize latent images. The latent image CTP printing plates may be referred to as “low-contrast,” “processless” or “semi-latent image” printing plates. This type of CTP printing plate is referred to herein as latent image CTP printing plate. Latent images may not be readily visible to the naked eye and in some circumstances may be almost invisible, or completely invisible, to the naked eye. Methods for targeting latent image CTP printing plates that employ illumination sources in the visible spectrum to render the images “visible to the naked eye” are typically not successful or useful for targeting latent images on a latent image CTP printing plate because the user is unable to visualize or sight the latent image target area to measure the dot coverage on the target area. Therefore, it is difficult to sight a dot coverage test device, for example, over the target area of the printing plate to measure the size, spacing or angle of the dots that make up the printed image.
In view of the foregoing issues, there may be a need for improved methods, apparatuses and systems in various configurations for targeting, measuring and/or otherwise analyzing dot density or dot coverage on various measurable media including latent image CTP printing plates.